CN-117732372-B - Method for synthesizing cubic boron nitride by using composite catalyst

Abstract

The invention relates to a method for synthesizing cubic boron nitride by using a composite catalyst. According to the method, hexagonal boron nitride h-BN with proper particle size is selected as a raw material, a mixture of high-entropy alloy FeCoNiCrCu and elemental metal Al is used as a composite catalyst, and after fully mixing and tabletting, cubic boron nitride c-BN is synthesized under the conditions of high temperature and high pressure, and yellow c-BN crystals can be obtained through acid-base purification. The composite catalyst is suitable for large-scale production, can effectively reduce the synthesis condition of the c-BN, and has good application prospect in the aspect of synthesizing the high-quality c-BN as a novel catalyst.

Inventors

• GAO WEI
• YUAN YANG
• LI JINYANG
• YIN HONG

Assignees

• 吉林大学

Dates

Publication Date

20260512

Application Date

20231217

Claims (3)

1. 1. A process for synthesizing cubic boron nitride by composite catalyst includes such steps as vacuum drying at 700 deg.C or less for 120min, high-entropy alloy FeCoNiCrCu and elementary metal Al as composite catalyst, weighing, mixing, hydraulic shaping, loading in heater, loading in pyrophyllite assembly block, loading in the chamber of domestic hexahedral top hydraulic press, holding at 5-5.5GPa and 1500-2000 deg.C for 5-30min, and acid-base purifying.
2. 2. The method for synthesizing cubic boron nitride by using the composite catalyst according to claim 1, wherein the content of each element in the adopted high-entropy alloy FeCoNiCrCu is equal in molar ratio, and the mass of the elemental metal Al accounts for 3% of the total mass of the composite catalyst.
3. 3. The method for synthesizing the cubic boron nitride by using the composite catalyst according to claim 1, wherein the adopted high-entropy alloy FeCoNiCrCu is obtained by a mechanical ball milling mode, wherein the mass ratio of balls to raw materials is 25:1, the balls are subjected to dry milling under an argon atmosphere at a rotating speed of 800rpm, each time of forward rotation is subjected to 5mins rest for 1min, and then the reverse rotation is subjected to 5mins rest for 1min, and the ball milling time is10 h.

Description

Method for synthesizing cubic boron nitride by using composite catalyst Technical Field The invention belongs to the technical field of superhard material synthesis, and particularly relates to a method for synthesizing cubic boron nitride crystals by using a composite catalyst. Background Cubic boron nitride (c-BN), diamond, siC, gaN and the like are called third generation semiconductor materials, have a crystal structure similar to diamond, have hardness inferior to that of diamond, and have good chemical stability, corrosion resistance, oxidation resistance, ultra wide band gap, high thermal conductivity, low dielectric constant at high temperature, so that the cubic boron nitride (c-BN) is superior to diamond in thermal stability, chemical inertness to ferrous metal and the like, and is widely applied to the fields of cutters, abrasive industry, high-precision metal processing and the like. In 1957, R.H. Wen Tuofu in the United states was first developed into c-BN, the excellent physicochemical properties of which have attracted extensive attention from researchers. In the synthesis process of c-BN, the method is mainly divided into a high-pressure synthesis method and a low-pressure synthesis method. The industrial large-scale synthesis of c-BN mainly adopts a high-temperature and high-pressure catalyst method, hexagonal boron nitride h-BN is used as a raw material, reaction conditions are reduced through the catalytic action of the catalyst, the h-BN is promoted to be converted into c-BN in a high-temperature and high-pressure environment, and crystal growth is carried out, so that the catalyst is another novel high-technology product appearing after the appearance of artificial diamond. The catalyst material can not only reduce the temperature and pressure required for synthesizing the c-BN, but also play a double role in dissolving the h-BN and catalyzing the conversion of the h-BN into the c-BN. Therefore, the type and quality of the catalyst material may have an important influence on the conversion rate, the crystal form, the impact strength and the particle size distribution of the c-BN. At present, alkali metal, alkaline earth metal, nitrides, borides, nitrogen borides and the like are often used as catalyst materials, and the catalyst materials are active in chemical property, extremely easy to oxidize and store, have high environmental requirements and other adverse factors in actual operation, so that the conversion rate of c-BN and the synthesis of high-quality c-BN are affected. Because of the important impact of catalysts on c-BN synthesis, new catalyst materials have been explored to improve their chemical stability to ensure that high quality c-BN materials are obtained. Disclosure of Invention The invention provides a method for synthesizing cubic boron nitride by taking high-entropy alloy FeCoNiCrCu and elemental metal Al as composite catalysts. The prepared high-entropy alloy FeCoNiCrCu with a specific proportion is mixed with elemental metal Al to be used as a novel composite catalyst, and the novel composite catalyst is used for high-temperature high-pressure compression of h-BN to c-BN, so that the defects in the prior art are overcome. In order to achieve the above purpose, the specific technical scheme of the invention is as follows: 1. And obtaining the high-entropy alloy FeCoNiCrCu by adopting a mechanical ball milling mode. Iron powder, cobalt powder, nickel powder, chromium powder and copper powder are weighed according to the equimolar ratio and are put into a ball milling tank together, wherein the mass ratio of grinding balls to metal mixed powder is 25:1, the grinding balls and the metal mixed powder are subjected to dry milling under the argon protection atmosphere at the rotating speed of 800rpm, each time of forward rotation is 5 minutes for rest for 1min, each time of reverse rotation is 5 minutes for rest for 1min, the reciprocating alternating circulation is carried out, and the ball milling time is 10h. 2. High-entropy alloy FeCoNiCrCu and elemental metal Al are selected as composite catalysts, wherein the mass of the metal Al accounts for 3% of the total mass of the composite catalysts. 3. The h-BN with proper particle size is selected as a raw material, and vacuum drying is carried out for 120min at the temperature of not more than 700 ℃. 4. The material taking h-BN and the composite catalyst are respectively weighed according to the mass ratio of 1:1.3 and are fully mixed. 5. The mixed materials are pressed into a cylinder shape through a hydraulic press, are filled into a graphite heating device and sleeved into a pyrophyllite assembly block, and are integrally put into a domestic hexahedral top hydraulic press chamber, and are subjected to heat preservation for 5-30min at the pressure of 5-5.5GPa and the temperature of 1500-2000 ℃. 6. The synthesized sample is crushed, and acid-base purified to obtain c-BN crystal, the color of the c-BN crystal is amber to y